WO2017153428A1 - Dispositif de dephosphoration - Google Patents
Dispositif de dephosphoration Download PDFInfo
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- WO2017153428A1 WO2017153428A1 PCT/EP2017/055358 EP2017055358W WO2017153428A1 WO 2017153428 A1 WO2017153428 A1 WO 2017153428A1 EP 2017055358 W EP2017055358 W EP 2017055358W WO 2017153428 A1 WO2017153428 A1 WO 2017153428A1
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Definitions
- the invention relates to a material for coating a device, in particular an induction furnace, dephosphorizing a ferrous metal, in particular a steel and / or a cast iron.
- the invention also relates to such a device.
- State of the art
- the purpose of the dephosphorization is to eliminate the phosphorus contained in ferrous metals. It is obtained by an oxy-reduction, optionally combined with an oxygen insufflation via a lance and / or an insufflation of neutral or reducing gas via an insufflation device at the bottom of the oven, as described, for example, by CN102936638 .
- an induction furnace for the dephosphorization rather than a VOD ("Vacuum oxygen decarburization") or RH-OB ("Ruhrstahl-Heraeus Oxygen Blowing”) furnace or an arc furnace , allows lower investment and higher flexibility. It also allows better control of the endothermic reaction related to dephosphorization.
- the rise in temperature of an induction furnace is also, advantageously, very fast. However, it requires higher performance refractory coatings to protect the area of the crucible that is in contact with the molten metal. Moreover, the corrosive environment preferably imposes coatings without joints. Brick walls are not the best suited.
- Figure 1 shows schematically, in cross section, a crucible of an induction furnace for dephosphorization.
- This crucible has a side wall 10 which extends, substantially vertically, from a bottom 12.
- the side wall 10 of the crucible conventionally comprises, from the outside to the inside of the crucible:
- a refractory lining 22 itself comprising an unconsolidated region 24, preferably in the form of a compacted powder, and a consolidated region 26, defining the inner surface 28 of the crucible.
- thermal insulation 18 and electrical insulation 20 are not limiting.
- the layer of electrical insulation 20 made of a dielectric mineral material, for example mica, and has the function of electrically isolating the inductor and the refractory lining.
- the thermal insulation layer 18 may in particular be a ceramic fiber mat, in particular an aluminosilicate.
- it makes it possible to compensate the effect of the thermal expansion of the refractory lining 22 during heating and / or to protect the layer of electrical insulation.
- the bottom 12 conventionally comprises, from the outside to the inside of the crucible:
- a refractory lining 22 'itself comprising an unconsolidated layer 24', preferably in the form of a compacted powder, and a consolidated layer 26 'defining the inner surface 28 of the crucible.
- the manufacture of the coating is carried out after having manufactured the sole 30 and the support layer 14, and having fixed the layers of thermal and electrical insulation.
- a powder of the material constituting the coating is first poured onto the upper surface of the hearth 30.
- the layer thus formed is then for example tamped or vibrated, until a thickness substantially corresponding to the thickness of the coating is obtained. above the sole.
- a mold is temporarily placed on the layer thus obtained.
- the mold is preferably shaped so as to extend substantially parallel to the surface defined by the layers of thermal and electrical insulation, while remaining spaced from a distance corresponding to the thickness of the coating of the side wall of the crucible.
- a powder of the material constituting the coating is then poured between the mold on the one hand and the surface defined by the thermal and electrical insulation layers on the other hand, preferably until the powder surrounds the mold over its entire length. height.
- the powder is shaped by compacting, preferably by vibration, optionally after adding a temporary binder. All known means for compacting a powder are possible.
- the compaction can be carried out as and when the starting load is paid.
- the temperature is then raised inside the crucible so as to consolidate at least a portion of the powder. If the powder contains a temporary binder or a heat activatable binder, raising the temperature will remove the temporary binder and activate the binder hot, without melting the refractory particles completely.
- the heating conditions make it possible to consolidate only part of the coating, which thus comprises a consolidated region, in the form of a layer on the interior side of the crucible, and an unconsolidated layer, in the form of a layer on the outside of the crucible.
- the mold can be removed after shaping the powder or after consolidation.
- the induction furnace is loaded with metal and / or precursors, for example pre-reduced iron ore.
- the metal resulting from the melting of the filler is then brought into contact with a basic dephosphorising slag.
- the temperature typically exceeds 1200 ° C., or even 1300 ° C. or 1400 ° C. during dephosphorization.
- the temperature is generally below 1700 ° C or 1650 ° C.
- Corrosion gradually wears the consolidated region. This wear therefore increases the amount of energy transmitted to the unconsolidated region, in particular by the molten metal and the slag. This results in a progressive consolidation of the unconsolidated region, as a result of said wear.
- the consolidated region is thus permanently reconstituted, downstream of the thermal flow, at the expense of the unconsolidated region. After complete “consumption" of the unconsolidated region, the consolidated region is no longer reconstituted and its thickness is reduced. The coating must then be renewed.
- Induction furnaces having a dry mud coating or "DVC", in English “dry vibratable mix” or “dry refractory”, based on alumina-magnesia (spinel MgAlO i).
- Such a coating is said to be “basic” as opposed to so-called “acid” coatings based on silica.
- a silica-based coating has very little corrosion resistance in a dephosphorization furnace.
- a slag called “dephosphorization” is indeed strongly basic. It typically comprises compounds based on calcium and / or barium, for example in the form of fluoride or aluminate, with in general an addition of FeO in the form of mill scale. The silica of the coating thus reacts strongly with the slag.
- the environment of the coatings is therefore variable: during the melting of the metal, the coatings are initially in contact with an acidic slag resulting from the oxides contained in the raw materials. For the dephosphorization, they are put in contact with a very basic slag. This slag becomes progressively acidified during dephosphorization.
- a dry rammed earth results from the thermal consolidation of a "dry rammed" powder, that is to say of the DVC type, as described for example in EP 1 224 153.
- This powder unlike a concrete, can be implemented “dry”, that is to say without adding water or liquid binder, or, rarely, with a very small amount of water or liquid binder (typically less than 3%) .
- a dry mud powder conventionally comprises no hydraulic binder, that is to say, able to take in mass by adding water.
- a dry mud powder consists of refractory particles and particles of a heat-activatable binder.
- the consolidation heat treatment temperature is between the melting temperature of the heat-activatable binder and that of the refractory particles.
- the heat-activatable binder can thus pass from the solid state to a viscous liquid state allowing adhesion to the refractory particles and a bond between them.
- the change from the solid state to this viscous liquid state is called "activation" of the binder.
- the heat-activatable binder is also chosen so that it can be in this viscous liquid state at a temperature close to the operating temperature of the oven, in particular during the first temperature rise.
- This viscous liquid state thus advantageously makes it possible to reduce the rigidity of the consolidated product, facilitating its deformation and thus increasing its ability to adapt to local thermomechanical stresses. During subsequent rise in temperature, this liquid state can be modified, and in particular become rigid by enrichment with fine particles.
- the consolidated product consists of a refractory granulate bound by a matrix. Its thermomechanical behavior is superior to that of concrete. Furthermore, a dry mud coating can be advantageously free of joints, unlike a brick or block assembly. But the joints are privileged zones of infiltration of metal. The absence of joint is particularly advantageous in an oven provided with a water-cooled inductor.
- JP 3 183 656 discloses dry mud powders based on crystalline silica.
- the sintered products obtained from these powders have the advantage of good resistance to thermal shocks, especially during repetitive temperature rise and fall.
- these sintered products exhibit limited resistance to corrosion and infiltration by molten metals. They put also hygiene problems during their establishment and disassembly, particularly because of the potential presence of crystalline silica dust.
- CN101717842 discloses a dephosphor induction furnace equipped with a refractory coating based on alumina-magnesia. This coating can be advantageously obtained by sintering in situ, at a temperature below 1600 ° C, a shaped starting charge. However, its resistance to corrosion is unsatisfactory.
- the permanent thermal deformation is the non-reversible variation of the dimensions of the coating resulting from the consolidation of the shaped feedstock, for example by sintering, and a return to ambient temperature. This deformation can be measured according to the recommendation EN-993-10.
- the ceramic material of CN101717842 has a very high permanent thermal deformation, from + 2% to + 6%.
- the initial operation of heating the oven coated with this type of material however leads to microfissurations and imperfect consolidation of the refractory lining.
- a dephosphorization furnace operates classically discontinuous, typically with a weekly stop, or even daily.
- the permanent thermal deformation is greater than 3%, the conduct of the heating operations is difficult.
- the sinterings resulting from successive fusions lead to swelling in the not yet consolidated region of the coating. This swelling can strongly damage the previously consolidated area.
- the coating of a dephosphorization furnace must therefore meet a number of specific constraints: resistance to the acidic environment of the slag, resistance to the very basic environment of the dephosphorising slag , resistance to thermal cycling, resistance to high temperatures: typically 1650 ° C-1700 ° C, resistance to abrasion and impact, resistance to thermal shock, resistance to rapid temperature rise, ...
- the invention proposes a material, in particular in the form of a powder, called “powder according to the invention", or of a consolidated product, called “consolidated product according to the invention", said material having the average chemical composition following, in percentages by mass on the basis of the refractory oxides and for a total of 100%:
- the sum of the oxides Al 2 O 3 + Cr 2 O 3 + Fe 2 O 3 + ZrO 2 + TiO 2 representing more than 80%, preferably more than 85%), preferably more than 90%, preferably more than 95%, preferably more than 97% of said composition chemical.
- such a material is particularly advantageous for the manufacture of a coating of a dephosphorization device. Its composition, which contains little magnesia, but necessarily chromium oxide, considerably improves the life of the coating when in contact with a molten ferrous metal being dephosphorized.
- the mass content of ⁇ 3 ⁇ 4 ⁇ 3 is less than 60%, preferably less than 50%, preferably less than 25%, preferably less than 20%, preferably less than 15%, preferably less than 12%, preferably less than 10%>;
- the Fe 2 O 3 content is less than 3%, preferably less than 2%, preferably less than 1%, preferably less than 0.5%;
- the TiC content is less than 7%, preferably less than 5%, preferably less than 3%;
- the TiC content is greater than 0.5%, greater than 1%, greater than 1.1%, greater than 2%, which promotes the formation of the alumina-chromium phase and confers improved corrosion resistance; ;
- the ZrC content is less than 20%, preferably less than 10%, preferably less than 5%, preferably less than 2%, preferably less than 1%, preferably less than 0.5%;
- the material comprises a hot-activatable binder selected from the group consisting of boron oxide, boric acid, borates, cryolite, fluoride salts, silicate compounds, phosphate compounds, feldspars, magnesium chlorides, colemanite, clay, kaolin, crystalline silica, amorphous silica, in particular silica fume, organic resins, especially phenolic resins, furan resins, ceramic frits, and mixtures thereof;
- a hot-activatable binder selected from the group consisting of boron oxide, boric acid, borates, cryolite, fluoride salts, silicate compounds, phosphate compounds, feldspars, magnesium chlorides, colemanite, clay, kaolin, crystalline silica, amorphous silica, in particular silica fume, organic resins, especially phenolic resins, furan resins, ceramic frits, and mixtures thereof;
- the material consists, for more than 95% by mass percentage, of refractory oxides, hot-activatable binder, optionally anti-dust agent, optionally anti-wetting agent chosen from silicon carbide, SiAlON, and nitrides, and impurities;
- the refractory oxides represent more than 80%, preferably more than 85%, preferably more than 90% of the mass of the material;
- the amount of impurities is less than 2%, less than 1%, less than 0.5%, or even substantially zero, in percentages by weight;
- the material has no hydraulic binder or organic binder; the material comprises:
- an anti-wetting agent selected from silicon carbide, SiAlON, nitrides, and / or
- an anti-dust agent selected from the group consisting of oils, in particular mineral oils, kerosene, organic polymers and mixtures thereof;
- the material is in the form of a powder, all the refractory particles representing more than 70%, preferably more than 80%, more than 90% of the mass of the material; the material is in the form of a consolidated product obtained by a consolidation heat treatment of a powder according to the invention, in particular in the form of a block or a coating, preferably in the form of a coating; the consolidated product has an open porosity preferably greater than 10%, preferably greater than 10%, preferably greater than 10%, preferably greater than 15%, and / or less than 30%, preferably less than 25%; preferably less than 20%.
- the material comprises more than 60% AhC, less than 1% silica, and, in a specific embodiment, more than 1% TiC.
- the invention also relates to a dephosphorization device, preferably a dephosphorization oven, preferably a dephosphor induction induction furnace, of a molten ferrous metal, said device comprising a refractory coating of which at least one region is made of a material according to the invention. 'invention.
- a dephosphorization device may be a metallurgical conversion equipment capable of carrying or keeping the metal to be dephosphorized.
- a treatment ladle in particular of steel or cast iron
- a dephosphorization oven preferably an intermittent furnace, in particular a well furnace, a crucible furnace, a furnace fixed hearth, a hearth furnace or an induction furnace, preferably an induction furnace.
- dephosphorizing agents are supplied to the molten metal, which leads to the formation of a dephosphorizing slag.
- a device, and in particular an oven, according to the invention may also comprise one or more of the following optional features:
- the material is preferably in the form of a consolidated product obtained by consolidation of a powder according to the invention, in particular when it is in a region intended to be in contact with said molten ferrous metal;
- the coating covers, at least in part, a crucible of the device
- the coating comprises a layer of consolidated material, in contact with the molten ferrous metal and / or with a dephosphorizing slag, and / or a powder material, said consolidated and powdered materials being in accordance with the invention;
- the material covers the region of the coating in contact or likely to be in contact with the dephosphorizing slag;
- the solid elements constituting a powder are called “particles”.
- the particles of the matrix fraction are called “fine particles” and the granular particles are called “grains”.
- the "size" of a particle is conventionally given by a particle size distribution characterization.
- a laser granulometer can measure sizes of up to 5 mm.
- the percentiles or "percentiles" (Dio), 50 (D50), 90 (D90) and 99.5 (D99, s) of a powder are the particle sizes corresponding to percentages, by mass, of 10%, 50 %, 90% and 99.5%, respectively, on the cumulative particle size distribution curve of the powder particles, the particle sizes being ranked in ascending order. For example, 10%, by weight, of the particles of the powder have a size smaller than Dio and 90% of the particles by mass have a size greater than Dio. Percentiles can be determined using a particle size distribution using a laser granulometer.
- the “maximum size” is the 99.5 percentile (D99, s) of said powder.
- the so-called “median size” is the percentile D50, that is to say the size dividing the particles into first and second populations equal in mass, these first and second populations comprising only particles having a larger size, or smaller respectively, at the median size.
- impurities is meant the inevitable constituents introduced involuntarily and necessarily with the raw materials or resulting from reactions with these constituents. Impurities are not necessary constituents, but only tolerated.
- refractory is meant “having a melting temperature greater than 1500 ° C.” This definition is commonly used by those skilled in the art and cited in “Refractory materials and technical ceramics (ceramics and technology elements)", G. Aliprandi, Editions Septima Paris, 1979. This book also gives pages 297 to 301 of examples of refractory materials, in particular oxides, carbides and nitrides.
- consolidation is meant a heat treatment, for example sintering and / or activation of a hot-activatable binder, leading to a stiffening of a feedstock, typically a shaped powder.
- heat-activatable binder is meant a component which, under the effect of an increase in temperature, will liquefy in a viscous form suitable for agglomerating the particles of a refractory powder in which it is mixed.
- boric acid, potassium tetrafluoroborate and cryolite melt at melting temperatures between 150 and 300 ° C, about 530 ° C and 1010 ° C, respectively, giving viscous agents capable of agglomerating the particles of a powder according to the invention, that is to say capable of leading to a structured product
- borate is meant a compound of oxoanions based on boron and electropositive elements.
- the oxoanion based on boron may be borated oxoanion BO2 " , oxoanion diborate B2O5 4 , oxoanion triborate B3O5 " , oxoanion tetraborate B4O7 2 ", sodium tetraborate Na2B4O7, lithium triborate L1B3O5, magnesium diborate Mg 2 B 2 O 5 are examples of borates Borates can also be hydrated, for example borax Na 2 B 4 O 7 ⁇ 10 ⁇ 10H 2 O.
- Temporal means "removed from the product during consolidation heat treatment”.
- a phase is called "minority" when another phase with a higher mass content is present.
- a powder according to the invention preferably comprises more than 70%, preferably more than 80%, more than 90%, preferably substantially 100% of refractory particles, a particle of said powder being classified in the fraction called "matrix fraction” or in the fraction called “granulate” according to whether it has a size less than or equal to 200 ⁇ , or greater than 200 ⁇ , respectively.
- a powder according to the invention can be manufactured by mixing raw materials having granulometries and suitable compositions.
- the refractory particles may in particular be sintered or melted particles.
- the matrix fraction represents more than 10%, more than 15%, preferably more than 20%, and / or less than 40%, preferably less than 35% of the mass of the powder, the 100% complement. being, by definition, constituted by the aggregate.
- the powder comprises more than 10%, more than 20%, or even more than 30% and / or less than 50%, or even less than 40% of particles having a size greater than 1 mm.
- the powder comprises more than 10%, more than 20% or even more than 30%, and / or less than 50%, or even less than 40% of particles having a size of between 0.1 mm and 1 mm. .
- the powder has the following characteristics:
- the maximum particle size is less than 5 mm
- the quantity of particles greater than 300 ⁇ is greater than 50% and less than 70%
- the amount of matrix fraction is greater than 15%, preferably greater than 20%, and less than 40%, and
- the quantity of particles smaller than 75 ⁇ is greater than 10% and less than
- the particle size distribution of a powder according to the invention is adapted to promote its compaction.
- Compaction models such as the Fuller-Bolomey model or the Andreassen model can be used to determine the most suitable particle size distribution.
- the refractory particles and the particles of the heat-activatable binder together represent more than 81%, more than 85%, more than 90%, more than 93%, even more than 95%, or even more than 98% of the mass. powder.
- a powder according to the invention is formed by the single mixture of refractory particles and hot-activatable binder particles.
- the material preferably in powder form, comprises:
- more than 80%, more than 90%, preferably substantially 100% by number, of the refractory particles are substantially pure, that is, each is more than 80% %, more than 95%, more than 99%, or even substantially 100% of their mass, of the same refractory oxide.
- the content of P 2 O 5 and / or of alkaline oxides K 2 O + Na 2 O is less than 1%, preferably less than 0.5%.
- these oxides are impurities.
- the heat-activatable binder must be chosen to be activatable at a temperature below the operating temperature.
- the heat-activatable binder must also be selected so as to have a lower melting temperature than the refractory particles. During the consolidation heat treatment, the heat-activatable binder can thus pass from the solid state to a viscous liquid state allowing adhesion to the refractory particles and a bond between them.
- the powder comprises more than 0.1%, and / or less than 5%, preferably less than 3%, or even less than 1% of heat-activatable binder.
- more than 80%, more than 90%, or even substantially 100% of the particles of the heat-activatable binder are in the matrix fraction, in weight percent based on the mass of the heat-activatable binder.
- the hot-activated binder has a melting temperature of greater than 5 ° C., preferably greater than 15 ° C., preferably greater than 20 ° C., or even greater than 30 ° C., greater than 50 ° C. , greater than 70 ° C, greater than 80 ° C, greater than 150 ° C, and / or less than 1500 ° C, less than 1300 ° C, or less than 1200 ° C.
- the heat-activatable binder has a melting temperature of between 150 ° C and 1200 ° C.
- the heat-activatable binder is not a metal.
- the heat-activatable binder is preferably selected from the group consisting of boron oxide, boric acid, borates, cryolite, fluoride salts, silicate compounds, phosphate compounds, feldspars, magnesium chlorides, colemanite, clay, kaolin, crystalline silica, amorphous silica, in particular silica fume, resins, ceramic frits, and mixtures thereof.
- the resin may in particular be chosen from phenolic resins, furan resins, acrylic resins, polyester resins, epoxy resins, silicone resins, siloxane resins, alkyd resins, polyvinyl resins, and mixtures thereof.
- the resin is chosen from particulate products convertible into a polymer during the consolidation heat treatment.
- the hot-activatable binder is selected from the group consisting of sodium borates, potassium borates, calcium borates, boric acid, boron oxide, clay, fluoride salts, and their mixtures.
- the heat-activatable binder is selected from the group consisting of boric acid, boron oxide, clay, fluoride salts, and mixtures thereof.
- the heat-activatable binder is inorganic.
- the powder may in particular comprise more than 0.1%, and / or less than 5%, preferably less than 3%, or even less than 1% of heat activatable binder, and in particular clay and / or boric acid.
- the powder contains an agent that makes it possible to reduce, or even eliminate, the dust during the setting up of the powder.
- This "anti-dust agent” can be chosen from the group formed by oils, in particular mineral oils, kerosene, organic polymers and their mixtures. Preferably this agent is kerosene. Preferably, the amount of anti-dust agent is between 0.1% and 1%.
- the powder contains at least one agent for reducing the wettability to the molten metals of said powder and / or the consolidated product obtained from said powder.
- this "anti-wetting agent” is selected from silicon carbide, SiAlON, nitrides.
- this agent is chosen from silicon carbide.
- the anti-wetting agent is introduced in the form of particles having a size less than or equal to 100 ⁇ .
- the amount of anti-wetting agent is between 5% and 15%, preferably between 5% and 10%.
- the powder consists of more than 95%, or even more than 98%, or even substantially 100%, of refractory particles, particles of heat-activatable binder, optionally particles of anti-dust agent and optionally particles of anti-wetting agent, the 100% optional supplement consisting of impurities, for example iron from a grinding stage.
- the powder does not contain a hydraulic binder or organic binder except, optionally, a resin.
- the powder contains neither hydraulic binder nor organic binder.
- the powder contains no hydraulic binder or organic binder except, optionally, a resin.
- the powder contains neither hydraulic binder nor organic binder.
- the refractory particles are preferably selected so that they can be consolidated, preferably sintered, to a temperature of at least 1000 ° C in the absence of a heat activatable binder.
- the granulate may also include one or more of the following optional features:
- the quantity of grains larger than 300 ⁇ m is preferably greater than 30%, greater than 40%, even greater than 50%, and / or less than 70%.
- the granulate comprises, or consists of, refractory grains of a material selected from the group consisting of aluminas, magnesia, chromium oxide, magnesia-chromites, bauxite, zirconia, partially zirconia stabilized zirconia, alumina-zirconia, magnesia-alumina spinel, zircon, cordierite, aluminum titanate, alumina-zirconia-silica-chromium oxide (or "AZS-Cr”) materials, bauxite, zirconia reinforced with alumina, and mixtures thereof.
- aluminas magnesia, chromium oxide, magnesia-chromites, bauxite, zirconia, partially zirconia stabilized zirconia, alumina-zirconia, magnesia-alumina spinel, zircon, cordierite, aluminum titanate, alumina-zirconia-silica-chromium oxide (or "AZ
- said refractory grains are of a material selected from the group consisting of white corundum, tabular alumina, brown corundum and black corundum, preferably from the group consisting of white corundum and tabular alumina.
- the maximum grain size is less than or equal to 10 mm, preferably less than or equal to 8 mm, preferably less than or equal to 6 mm, or even less than or equal to 4 mm.
- the granulate preferably comprises less than 20%, less than 10%, or even less than 5%, or substantially no particles of said hot-activatable binder, called “binder grains”, in percentages by weight on the basis of the powder.
- the matrix fraction may also comprise one or more of the following optional characteristics:
- the amount of fine particles having a size of less than 75 ⁇ is between 10% and 35%, based on the mass of the material.
- the matrix fraction contains refractory fine particles of a refractory material selected from the group consisting of alumina, magnesia, chromium oxide, bauxite, zirconia, partially stabilized zirconia, stabilized zirconia, mullite-zirconia , alumina-zirconia, magnesia-alumina spinel, zircon, aluminum titanate, alumina-zirconia-silica-chromium oxide (or "AZS-Cr") materials, bauxite, alumina-reinforced zirconia and their mixtures.
- a refractory material selected from the group consisting of alumina, magnesia, chromium oxide, bauxite, zirconia, partially stabilized zirconia, stabilized zirconia, mullite-zirconia , alumina-zirconia, magnesia-alumina spinel, zircon, aluminum titanate, alumina-zirc
- said refractory fine particles are made of a refractory material chosen from the group formed by alumina, mullite and clay chamottes containing between 30% and 50% of alumina, preferably between 35% and 45% of alumina. , bauxite, and mixtures thereof. More preferably, said refractory fine particles are each of alumina or chromium.
- the above-mentioned refractory fine particles together represent more than 80%, more than 90%, or even substantially 100% of the refractory fine particles of the matrix fraction. More than 80% or even more than 90% or even substantially 100% of the heat-activatable binder belongs to the matrix fraction, in percentage on the basis of the mass of the hot-activatable binder.
- the amount of heat-activatable binder fines is preferably greater than 0.1%, and / or preferably less than 5%, preferably less than 3%, preferably less than 1%, based on mass. of the material.
- the invention also relates to a method of manufacturing a consolidated product according to the invention comprising the following successive steps:
- the starting feedstock comprising a powder according to the invention optionally comprising a hot-activatable binder, the liquid phase in said feedstock representing less than 3%, preferably less than 2%, more preferably substantially 0% of the mass of the starting load; or (2) the feedstock consisting of a mixture comprising a powder according to the invention optionally comprising a hot-activatable binder, and water and / or a temporary binder, as described below;
- This method can be implemented for the manufacture of a coating of the side wall and / or the bottom of a crucible of an induction furnace.
- the water, or even the liquid phase in said feedstock preferably represents less than 2% of the mass of the feedstock. More preferably, and in particular for a crucible induction furnace coating, the feedstock does not have water or temporary binder.
- step b) the shaping results preferably from the implementation of a conventional method as described in the introduction to the present description.
- a powder according to the invention is preferably poured between a mold on the one hand and the surface defined by layers of thermal and electrical insulation and on the surface of the sole on the other hand.
- a rise in temperature then allows activation of the hot-activatable binder, that is to say allows the particles of hot-activatable binder to melt in a viscous form, and thus to ensure the cohesion of the refractory particles.
- the consolidation heat treatment is preferably carried out at a temperature above the operating temperature.
- the duration of the plateau at the maximum temperature reached during the consolidation heat treatment is preferably greater than 30 minutes, preferably greater than 1 hour, and / or less than 10 hours, preferably less than 3 hours.
- the consolidation heat treatment can lead to sintering of the refractory particles.
- the heat treatment leads to activation of the heat-activatable binder when present and / or sintering which generates (s) a binder phase between the refractory particles. This produces a so-called "consolidated" product.
- the open porosity of such a consolidated product is between 10% and 30%.
- the activation temperature has not been reached over the entire thickness of the side wall and bottom of the crucible, a portion of the crucible, particularly near the furnace inductor, may not be consolidated.
- the mold can be removed or melted.
- the crucible is then ready to serve for the melting of metal.
- This method of manufacturing a consolidated product can also be implemented for the manufacture of prefabricated or preformed unit blocks, in particular intended to be used as a consolidated region or to be assembled with other blocks.
- such a unitary block is a preformed crucible.
- a temporary binder for the manufacture of blocks, it is preferable, according to option (2), to add to the powder a temporary binder, and / or a hydraulic binder and water. This gives a mixture that can be poured into a mold and, after step b), to obtain a preform having, at room temperature, a holding, so-called "cold".
- the invention also relates to such a mixture.
- the amount of temporary binder in this mixture is greater than 0.5% and / or less than 6%, and the amount of water is greater than 2% and / or less than 6%, or even less than 5% , in percentages by weight relative to the mass of the powder before addition of the temporary binder and water.
- Temporary binders conventionally used for the manufacture of sintered ceramic blocks may be used, for example dextrin, calcium lignosulfonate, CMC, or PEG.
- the mass content of Cr 2 O 3 is less than 60%, even less than 50%, or even less than 20%, or even less than 15%; and or
- the Fe2O3 content is less than 5%>, less than 2%>, less than 1%>, or even less than
- the TiC content is less than 10%, less than 5%; and or
- the ZrC content is less than 30%, less than 10%, less than 5%, and even less than 2%.
- the dilatometric variations are reduced.
- the main phases are phases of corundum (alpha alumina) and spinel (MgAhC; MgC ⁇ C; FeCr2O4; FeAhO i).
- the chromium oxide is preferably predominantly present as a solid solution (Al, Cr) 203.
- a consolidated product according to the invention preferably comprises more than 0.1%, and / or less than 5%, less than 3%, less than 1%, of heat-activatable binder and / or transforming said hot-activatable binder resulting from said consolidation heat treatment.
- a consolidated product according to the invention preferably comprises more than 80%, more than 85%, more than 90% of oxides.
- the density of a consolidated product according to the invention is preferably greater than 3.0 g / cm 3 , and / or less than 3.7 g / cm 3 , preferably less than 3.5 g / cm 3 .
- the permanent thermal deformation, measured as in the examples below, of a consolidated product according to the invention is preferably less than 3.0%, preferably less than 2.5%, preferably less than 2%, 0%>, preferably less than 1.5%>.
- the cold compressive strength, measured as in the examples below, of a consolidated product according to the invention is preferably greater than 18 MPa, preferably greater than 25 MPa, preferably greater than 30 MPa, preferably greater than 40 MPa, preferably greater than 50 MPa.
- the device according to the invention is of the "crucible” or “coreless” type in English, as described in the introduction to the present description.
- the ratio of the upper diameter of the crucible to the height of the molten metal is preferably greater than 0.4, or even greater than 0.5 or even greater than 0.6, to maximize dephosphorization.
- the unconsolidated layer has the same chemical composition as the consolidated layer.
- the total thickness of the refractory lining is preferably greater than 5 cm, or even greater than 6 cm, or greater than 8 cm, and / or less than 30 cm, or even less than 25 cm.
- the consolidated layer defines the surface of the crucible in contact with the molten metal.
- the thickness of the consolidated layer is preferably greater than 5 mm, or even greater than 1 cm, or even greater than 2 cm.
- the thickness of the consolidated layer is preferably less than half that of the refractory lining.
- the composition and / or the structure of the refractory lining may be variable in the vertical direction.
- the lower part of the refractory lining of the crucible which extends from the bottom of the crucible to the height greater than one-third of the height of the crucible, or even up to the median height of the crucible, is made of a refractory material of DVC or rammed type, for example based on alumina-magnesium spinel.
- the intermediate portion of the refractory lining of the crucible which extends from the bottom to a height greater than the level of the dephosphoric slag, and which is in contact with the molten metal and / or with the slag, is in a consolidated product according to the invention.
- the upper part of the refractory lining of the crucible which extends from the intermediate part to the top of the crucible, is made of a monolithic material of concrete type, DVC or plastic mass.
- the consolidation of this material may advantageously be carried out at a temperature lower than that of the other zones which are in permanent contact with the metal and the molten slag.
- the device is heated to a temperature greater than 1450C, preferably greater than 1500 ° C, to ensure sintering of the consolidated region.
- the refractory lining extends to define an inner surface 28 of the crucible without a seal.
- the molten ferrous metal in the crucible may be a steel or a cast iron.
- the melt can be obtained in particular by direct reduction or from pre-reduced iron ore.
- white corundum powder having a median size of 1 mm, a minimum size of 75 ⁇ and a maximum size of 4 mm, having an alumina content greater than
- the density of the constitutive material of the particles being equal to 3.95 g / cm 3 ; white corundum powder having a size less than 200 ⁇ and a median size of 30 ⁇ ;
- pigmentary chromium oxide typically containing 98% by weight of (3 ⁇ 403, having a median D50 size of 0.3 ⁇ and a grain density of 5.0, marketed by BAYFERROX;
- magnesia powder (magnesium oxide) calcined, containing 97% by weight of MgO, the particle size being between 500 ⁇ and 4 mm, marketed by MAF
- powder of calcined magnesia containing 97% by weight of MgO, the maximum particle size being 200 ⁇ , the median size being 90 ⁇ , marketed by MAF Magnesite.
- the different particulate raw materials are introduced into a kneader, and mixed dry for 5 minutes.
- Example 1 the magnesia was mixed with calcined alumina and quartz sand in suitable proportions to obtain the mineral chemical composition shown in Table 1.
- Example 2 is obtained by substituting with white corundum a large part of the magnesia and all of the crystalline silica provided in the form of fine quartz sand used in the mixture of Example 1.
- Example 3 unlike the mixture of Example 2, a portion of the calcined alumina and fine calcined magnesia was substituted with an equivalent weight of chromium pigment oxide.
- Example 4 the level of chromium oxide is multiplied by more than 2.5 relative to Example 3 by replacing a portion of the calcined alumina.
- Comparative Example 6 has an even higher chromium oxide content. This was done by mixing a fraction of 0.2 to 2 mm obtained by crushing-grinding a known refractory product, called Zirchrom 90®, 18% alumina, 5% chromium oxide pigment and 3% ) of quartz sand. After homogenization of the mineral powders, 1% of dextrin powder is also added to a mixer, this percentage being relative to the mass of said powder. After 5 minutes of mixing, 3% water is gradually added, in percentage relative to the mass of the initial powder (thus excluding dextrin powder), without stopping the mixer. After introduction of all the water, mixing is continued for 5 minutes.
- a known refractory product called Zirchrom 90®, 18% alumina, 5% chromium oxide pigment and 3%
- a temporary binder such as dextrin and water are necessary for the manufacture of small samples, but are not required for industrial applications, particularly for forming a coating of an oven.
- the wet mixture poured into the molds undergoes uniaxial pressing at a pressure of 90 MPa.
- the preforms thus obtained are demolded and then dried for 24 hours at 110 ° C.
- the cylinder for measuring permanent thermal deformation is not heat treated.
- the chemical analysis is carried out by X-ray fluorescence spectroscopy for elements whose content is greater than 0.1% by mass. If the content of an element is less than 0, 1% by weight, it is determined by ICP (Induction Coupled Plasma) on a Vista AX model (marketed by Varian).
- ICP Induction Coupled Plasma
- the measurements of the bulk density and the open porosity after consolidation heat treatment are carried out according to the following method: the cylinders mentioned above are first weighed dry to determine their dry mass. They are then placed in a bell under vacuum for 30 minutes. The bell is then filled with water, so that the bars are completely immersed. After immersion, the vacuum is maintained for 30 minutes. Atmospheric pressure is then restored to the bell and allowed to stand for another 30 minutes. The samples are then subjected to hydrostatic weighing, giving a mass Mi. They are then wiped with a damp cloth and their wet mass Mh is measured.
- the apparent density is given by the ratio p.Ms/(Mh-Mi), in g / cm 3 , with p being the density of the water, taken equal to 1 g / cm 3 .
- the open porosity is given by the ratio 100 (Mh-Ms) / (Mh-Mi), in%.
- the measurement of the permanent thermal deformation is carried out, according to the standard EN993-10, by comparison of the dimensions of the cylinder between the "raw dry" state, that is to say preceding a heat treatment, and that after said heat treatment at 1600 ° C for 2 hours and return to room temperature.
- Corrosion resistance is evaluated in a laboratory induction furnace with a capacity of 250 kg of ferrous metal.
- the cylinder introduced into the furnace, is rotated axially at a linear speed of 10 cm per second (30 rpm) and then immersed for 20 minutes in a bath of molten ferrous metal at a temperature of 1580 ° C. at a depth of between 10 and 15 cm below the surface of the bath.
- the initial mass composition of the ferrous metal in molten metal is as follows: 0.2% C; 0.3% Si; 0.7% Mn and 0.08% P.
- the initial mass composition of the dephosphoric slag is as follows: 58.8% CaO, 10.6% CaF2 and 30.3% FeO.
- Alumina-magnesia type products such as those of Comparative Examples 1 to 3 have a permanent thermal deformation that is too high or a low resistance to corrosion.
- the tests show that the permanent thermal deformation is much lower with the examples according to the invention. The risk of cracking is reduced and the life of the coating increased. The thickness of the coating can also be reduced. The tests also show that the corrosion resistance for the intended application is improved with the examples according to the invention.
- Example 5 is the most preferred example. As now clearly apparent, the invention provides a material having good corrosion resistance, high mechanical strength and permanent thermal deformation of less than 5%, preferably less than 3%.
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Abstract
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FR3107896A1 (fr) * | 2020-03-05 | 2021-09-10 | Saint-Gobain Centre De Recherches Et D'etudes Europeen | Laitier de déphosphoration |
WO2021176024A1 (fr) * | 2020-03-05 | 2021-09-10 | Saint-Gobain Centre De Recherches Et D'etudes Europeen | Laitier de déphosphoration |
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CN113699317A (zh) * | 2021-09-08 | 2021-11-26 | 北京会盛百模具材料技术有限公司 | 脱磷炉、钢水脱磷方法和冶金工艺 |
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WO2014097219A1 (fr) * | 2012-12-19 | 2014-06-26 | Saint-Gobain Centre De Recherches Et D'etudes Europeen | Produit alumine-magnésie pour gazéificateur ou pour four métallurgique |
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FR3107896A1 (fr) * | 2020-03-05 | 2021-09-10 | Saint-Gobain Centre De Recherches Et D'etudes Europeen | Laitier de déphosphoration |
WO2021176024A1 (fr) * | 2020-03-05 | 2021-09-10 | Saint-Gobain Centre De Recherches Et D'etudes Europeen | Laitier de déphosphoration |
Also Published As
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CN108779032A (zh) | 2018-11-09 |
BR112018067830B1 (pt) | 2023-02-14 |
BR112018067830A2 (pt) | 2019-01-02 |
FR3048428B1 (fr) | 2020-09-25 |
FR3048428A1 (fr) | 2017-09-08 |
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